We wish to study the nature of biochemical interactions involved in DNA-DNA, and DNA-protein recognition. We also wish to understand the catalytic mechanism of DNA recombination. The site-specific recombination system of the 2 micron circle plasmid of yeast provides the opportunity to pursue both goals. The recombinase enzyme FLP recognizes a short, specific DNA sequence with a two fold axis of symmetry. The regions of the substrate involved in DNA-DNA interactions and protein-contacting have been mapped. Clues have been obtained concerning the chemistry of recombination. We plan to extend these studies using molecular genetic, biochemical, immunologic and structural approaches. We hope these investigations will reveal how a functional recombination complex is generated, and how strand cleavage, strand swapping, and ligation are effected during recombination. We would like to study the possible relevance of the recombination reaction to the physiology of 2 micron circle.